It is most satisfying ..

[Aryana]

Dear All!
Can anybody help me about this passage? The words in bold are intended:
"It is most satisfying to be able to conclude this book in the certain knowledge that it has shown the archival holdings to be surprisingly rich and deep – such a pleasant surprise – and that it has to a significant degree remedied all of the above-mentioned deficiencies."
The text is from a book about the Nazi Regime's espionage in Persia during World War II. Formerly, it was thought there are few documents about these attempts, and the book tries to show it is not so.
The passage is from this book:

Nazi Secret Warfare

in Occupied Persia (Iran)
The Failure of the German Intelligence
Services, 1939–45​

Adrian O’Sullivan

Many thanks in advance.

​

 

[The Newt]

[...]
"It is most satisfying to be able to conclude this book in the certain knowledge [...]

It would help us if you could be more specific about which of the above words you don't understand.

 

[Aryana]

Hi!
The words "conclude this book in the certain knowledge" is ambiguous. I guess it means "it will be very satisfactory if the author could finish this book while developing knowledge about richness of archives..." but I am not sure.

 

[The Newt]

Hi!
The words "conclude this book in the certain knowledge" is ambiguous. I guess it means "it will be very satisfactory if the author could finish this book while developing knowledge about richness of archives..." but I am not sure.

The idea is "it is very satisfying for me, the author, to finish writing this book and know for certain that it has shown..."